A balloon catheter is widely used to ameliorate lesion areas (stenotic lesions) generated in a body lumen of a living body. The balloon catheter typically includes an elongated catheter main body portion and a balloon provided on a distal side of the catheter main body portion. The balloon can be inflated in a radial direction (i.e., is inflatable to expand radially outward). The balloon catheter is configured such that the deflated balloon is advanced to a location of interest in a body via a narrow body lumen and then the balloon of the balloon catheter is inflated, whereby a lesion area in the living body can be widened.
The catheter main body portion includes a hollow outer tube and a hollow inner tube. The inner tube is disposed within a hollow interior of the outer tube. A distal-side end portion of the outer tube is fixed to a proximal side of the balloon and the hollow interior of the outer tube forms an inflation lumen that communicates with the interior of the balloon. The balloon can be inflated by infusing an inflation fluid into the balloon via the inflation lumen at the time of treatment (i.e., when the balloon is positioned at the lesion area). A distal-side end portion of the inner tube is fixed to a distal side of the balloon, and a hollow interior of the inner tube forms a guide wire lumen into which a guide wire can be inserted.
The treatment by the balloon catheter is conducted in the following manner. First, the guide wire is inserted into a body lumen of a living body to pass through a lesion area. The balloon catheter is then inserted into the body lumen along the guide wire (i.e., the balloon catheter is moved into the living body along the guide wire) to deliver the balloon to the lesion area. The balloon is inflated at the lesion area, thereby proceeding with the treatment (e.g., widening the stenosis region of the body lumen). Subsequently, the balloon is deflated (subjected to deflation) and the balloon catheter is removed from within the body.
A manipulation (i.e., operations) of inflating and then deflating the balloon and inflating the balloon again at the same location, or a manipulation (i.e., operations) of inflating the balloon in one lesion area, then deflating the balloon, moving the balloon to another lesion area, and inflating the balloon again is often performed depending on a state of the lesion area or the number of lesion areas.
As described above, balloon catheter operations include inserting the balloon catheter into a narrow body lumen, moving the balloon catheter, and withdrawing the balloon catheter from the living body. Therefore, a balloon catheter needs to exhibit an excellent passing performance for moving within the body lumen (i.e., movability or maneuverability within the body lumen). Since an outer diameter of the balloon of the balloon catheter is relatively large, the balloon must be deflated (i.e., in a tight state against the catheter main body portion) as much as possible. The balloon is thus collapsed during deflation into a shape with a contact portion in contact with the inner tube and a plurality of vane portions protruding from the contact portion in a radial direction.
When the balloon is inflated and then deflated, the balloon returns to this original shape with the contact portion and the vane portions. When the inflation and the deflation operations are repeated, however, the balloon in the deflated state often loses the shape (i.e., the shape with the contact portion and the vane portions). For example, the original shape of the balloon in the deflated state may be one that has three vane portions that are each disposed at an angle of 120 degrees in a circumferential direction (i.e., the three vane portions are evenly spaced apart in the circumferential direction). Contact portions are provided between the vane portions. When a balloon of this configuration is repeatedly inflated and deflated a plurality of times, the contact portions do not completely return to original shapes and the adjacent vane portions may become connected together, so that the shape of the balloon often changes over time to a shape with two vane portions. Decreasing the number of vane portions causes the protrusion length of one vane portion to increase. Moreover, the shapes of the vane portions become uneven because of the difference of the number of vane portions from the original number. As a result, an outer diameter of the balloon of the balloon catheter increases, resulting in the degradation of the passing performance (i.e., maneuverability) of the balloon catheter.
As outlined by the above discussion, a balloon catheter is required to exhibit excellent re-wrappability to help ensure that the balloon returns to the original shape when being deflated after inflation. Japanese Patent Application Publication No. 2002-336359 discloses an example of a technique for attaching a metallic external member including a band and fingers to a balloon from outside and disposing the fingers at positions of contact portions. The fingers can compress the contact portions to return the contact portions to the original positions when the balloon is deflated.